The rate of change indicator (VVI) is normally displayed in what units?

• A. Meters per second
• B. Knots
• C. Feet per minute
• D. Liters per minute

Answer: (C)

The main idea here is how vertical speed is shown. The VVI indicates how fast you’re changing altitude per unit time—the rate of climb or descent. In aviation, altitude is referenced in feet, so the rate is normally displayed as feet per minute. This unit makes it easy to judge how quickly you’ll reach a target altitude and to coordinate vertical profiles with ATC and procedures. Other units don’t fit this purpose: meters per second isn’t the standard in most aviation contexts for VVI, knots measure horizontal speed, and liters per minute is fuel flow, not altitude change. So feet per minute is the appropriate, conventional display for the rate of change of altitude.